Question

Endangered plant species are conserved through
A. Herbarium
B. Cryopreservation
C. Gene bank
D. Tissue culture

Answer 1

There are numerous approaches to save endangered species of both plants as well as animals, which are currently in practice.
One of the very common approaches is making or building safe areas, captive propagation and transferring one species back into an earlier environment, as well as increasing awareness for conservation in community.

Complete answer:
Cryopreservation, gene banks and tissue culture are all ex-situ methods of conservation of biodiversity. In this method, vulnerable species of animals and plants are brought out from their own natural habitat and are cited in exceptional locations to be kept safe and taken care of.
Gene banks help a lot in conserving the genetic material of endangered species. In the case of plants, this can be done by in vitro storage, freezing cuttings obtained from the plant, or stocking the seeds, such as in a seed bank. All this process of conservation is called ex- situ conservation.
Herbarium is usually known to be an assemblage of conserved plant samples and related facts, further used for systematic study. In herbarium, the specimens are usually in dried form, and mounted on paper which is also called exsiccatae. Although sometimes, with respect to the material, the sample or specimen may possibly be kept in containers or stored in preservatives like alcohol.

Hence, the correct answer is Gene bank.

Note: Ex-situ conservation is nothing but a process that involves conserving wildlife outside of their own natural habitats.
Gene banks are of several types- tissue banks, seed banks, cryobank and field gene bank.